There are people who have actual organic problems, such as brain tumors, which may cause or be accompanied by anger of some intensity. But of course, nobody with a brain tumor would be diagnosed as "mentally ill" for it, nor would a psychiatrist be the specialist to treat it.

There is no medical test in existence for depression, anxiety, bipolar disorder, obsessive-compulsive disorder, or intermittent explosive disorder. None are even proposed for these, or for the new temper dysregulation disorder, or for any other mental disorder, in DSM-V. The only tools for diagnosis of mental disorder are direct and indirect observation of behavior and evaluation of self-reports by patients.

Whether anger of any type or intensity is "mental illness" is ultimately a subjective, if not arbitrary, evaluation. One professional can say anger is an illness in a particular case, or that it is always an illness; another equally qualified professional can say with equal evidential basis that the same anger is just bad behavior, or that anger itself is never an illness. Nobody can prove, scientifically, which expert is "right" because there isn't any right or wrong about it. It's not even a matter of opinion, really. It's pure semantics. People can speculate and agree or disagree or abstain on this according to whim.

Even worse, it will always be so, because "mental illness" itself has no objective definition based in any physical/biological reality. It's a metaphor, merely reflecting our indomitable hope and desire that we might someday be able to fix people up, rather than just fight or punish them.

Melinda Beck has sufficient training and education to know this. Her article is misleading, definitely not educational or a public service. It's no better than average entertainment.